This invention relates to a bearing and drive for a horizontally arranged open-end spinning rotor unit that has a rotor and a rotor shaft that is disposed in wedge-shaped gaps of two pairs of supporting disks axially spaced from one another along the rotor shaft. The rotor shaft is driven by a moving tangential belt which engages the rotor shaft between the pairs of supporting disks. The tangential belt is loaded in the direction of the wedge-shaped gap by a tension roller arranged between the pairs of supporting disks in proximity of the rotor shaft. The tension roller can be lifted off the tangential belt via an actuating member for interrupting the drive, and also for making it possible to apply a braking member to the rotor shaft.
Bearings and drives of the above noted type are disclosed in German Pat. (DE-PS) No. 19 01 453 and German Published Examined Application (DE-AS) No. 21 41 276 which are suitable for use with rotor speeds up to about 80,000 revolutions per minute. This type of bearing and the pertaining drive is a very complex vibration system because the supporting disks are equipped with a spring-like elastic fittings and also because the tangential belt, via the tension roller, is elastically pressed against the rotor shaft. In addition, accumulations of fiber material and/or direct within the spinning rotor occur eccentrically with respect to the rotor shaft. By means of a construction, especially a stronger construction of the rotor shaft of the open-end spinning rotor, it is provided that the operating speed is sufficiently below the critical rotational speed (rotational speed inducing harmful resonant harmonic vibrations) of the system. In such a case, the critical speed is only relatively difficult to determine and may also possibly change during operation by fiber material accumulation with the spinning rotor.
Currently, in the rotor spinning industry speeds of more than 100,000 min -1 revolutions per minute are preferred, which further increases the problem of the critical speed. In order to solve this problem and especially to avoid a stronger dimensioning of the rotorshaft, which would require a stronger dimensioning of the supporting disks and bearings resulting in an increased power consumption, it is disclosed in German published patent application (DE-OS) No. 33 24 129 and corresponding pending U.S. patent application Ser. No. 627,559, filed July 3, 1984, now U.S. Pat. No. 4,667,464, to develop the system in such a way that the operating speed of the open-end spinning rotor is above the critical speed. In this construction, difficulties may occur because at the starting time, the first critical speed located at a relatively low speed is passed through rapidly, whereas the second higher critical speed is not passed as rapidly so that vibration problems may occur.
It is an object of the present invention to provide a bearing and a drive arrangement of the type mentioned above which will facilitate operation with rotational speeds of more than 100,000 revolutions per minute, below a critical speed, without resulting in an increased expenditure of material and without disproportionately increased power consumption.
This objective is achieved by providing a braking member which has at least two brake shoes that can be applied to the rotor shaft essentially radially and essentially horizontally from the direction of two sides and which is arranged below the tangential belt. Further, the supporting disk pairs are arranged at a clear distance (axial spacing of respective axially facing surfaces of the disks of the disk pairs) from one another that corresponds to the axial width of the tension roller plus a tolerance play.
In a preferred embodiment of the invention the clear distance between the supporting disk pairs is minimized, thereby moving the critical speed into a range of significantly higher speeds, without the necessity of strengthening the rotor shaft and/or the bearings of the supporting disks. With the decrease of the distance between the supporting disk pairs, it is also possible to reduce the length of the shaft of the open-end spinning rotor so that weight and power may also be saved at increased speeds.
A bearing and a drive for an open-end spinning rotor has been disclosed in German Published patent application (DE-AS) No. 25 25 435, in which the rotor shaft is disposed in wedged-shaped gaps of supporting disk pairs and is driven by a tangential belt moving between the supporting disks. Further, braking means are arranged below the tangential belt. These braking means include brake shoes that are applied from below to the shaft of the open-end spinning rotor which lift the rotor shaft out of the wedge-shaped gap and press it against two slide bearings. In this construction, a tension roller loading the tangential belt is provided which is located at a distance from the rotor shaft and is arranged outside the range of the supporting disk pairs. As a result, space is created for a lifter pulley that can be applied to the tangential belt from below when the rotor shaft is lifted out. This pulley lifts the tangential belt off the rotor shaft during the stopping operation, because otherwise the belt would run against the rotorshaft that is lifted out of the wedge-shaped gap with increased pressure force. In this construction, the supporting disk pairs in the axial direction of the rotor shaft are arranged at a relatively large distance from one another in the axial direction of the rotor shaft in order to create a space in which the actuating means for the braking device are guided. In this construction, it is a disadvantage that the rotor shaft leaves the wedge-shaped gap because this results in increased stress to the supporting disk pairs during the starting as well as during the stopping operation. In addition, the arrangement of the tension roller is disadvantageous because the introduction of the driving force into the rotor shaft is impaired.
In another type of bearing disclosed in German Published Unexamined application (DE-OS) No. 33 46 843), the rotor shaft is disposed in the proximity of the spinning rotor with one pair of supporting disks. At the end of the shaft that faces away from the rotor the shaft is provided with a bearing that receives axial and radial forces and a braking device having two brake shoes. The braking device in this construction is arranged laterally staggered with respect to the tangential belt driving the rotor shaft in the proximity of the pair of supporting disks. The brake shoes are arranged on two arms that project over the rotor shaft and the tangential belt in upward direction. The brake shoes are applied in one direction radially to the rotor shaft and radially to the respective opposite supporting disks so that the rotor shaft is pressed into the wedge-shaped gap. When transferring such a braking device to a bearing with two pairs of supporting disks, the clear distance between the pairs of supporting disks would necessarily be increased by the braking device. In the case of such a transfer, it would also be necessary to provide two braking devices of this type on both sides of the tangential belt because it cannot be arranged in the center between the pairs of supporting disks.
In a further development of certain preferred embodiments of the invention, it is provided that the brake shoes are arranged on tong arms that can be pivoted around a pivot shaft arranged essentially vertically under the rotor shaft and extending in parallel to it. As a result, it is possible to apply the break shoes approximately horizontally to the rotor shaft from both sides. In an advantageous development of the invention, it is provided in this case that the brake shoes are provided with cup-shaped braking surfaces adapted to the rotor shaft. This ensures that the brake shoes grip the rotor shaft securely without pressing it with increased force against the linings of the supporting disks.
In a further development of certain preferred embodiments of the invention, it is provided that the actuating mechanism for the lifting-off of the tension roller is connected with the actuating mechanism for the actuating of the braking device via a springy intermediate element. As a result, despite having a joint actuating device, the lifting-off of the tension roller is functionally separate from the application of the braking device, so that the tension roller is always lifted off the tangential belt the same amount, even when the brake shoes become worn.
In the case of a practical construction of a preferred embodiment of the invention, it was found that the critical speed can be shifted sufficiently far into the range of high speeds, even when the operational speed reaches about 120,000 revolutions per minute, when the clear distance between the supporting disk pairs is no more than 1.8 times the width of the tangential belt. In the case of customary machine lengths and therefore the required power requirement for the drive of about 100 spinning rotors of one side of the machine, it has proven to be advantageous because of the dimensions of the tangential belt that the clear distance between the disks of the supporting disk pairs is no more than 45 mm.
In a further development of preferred embodiments of the invention, it is provided that the spinning rotor has a rotor shaft of a length of no more than 90 mm and a diameter of at least 7.5 mm and a rotor of a weight of no more than 0.7 N (Newtons which converts to 0.157367 pound weight). When the supporting disk pairs are arranged at a suitable distance, the result is an advantageous relationship for the bearing expenditures and for the required driving power while avoiding the critical speed.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment constructed in accordance with the present invention.